Method and apparatus for continuously degassing molten metals, particularly steel, by evacuation



July 7, 1959 A L R N 2,893,860

METHOD AND APPARATUS FOR CONTINUOUSLY DEGASSING MOLTEN METALS, PARTICULARLY STEEL, BY EVACUATION Filed Aug. 5, 1957 e sheets sneet 1 INVE N TOR ALBERT LORENZ ATTORNEYS y 7, 1959 L A. LORENZ 2,893,860

METHOD AND APPARATUS FOR CONTINUOUSLY DEGASSING MOLTEN METALS, PARTICULARLY STEEL, BY EVACUATION Filed Aug. 5, 1957 6 Sheets-Sheet 2 I ALBERT LORENZ A'i'rolglysrs July 7, 1959 LORENZ 2,893,860 METHQD AND APPARATUS FOR CQNTINUOUSLY DEGASSING MQLTEN METALS, PARTICULARLY STEEL, BY EVACUATION Filed Aug. 5, 1957 6 Sheets-Sheet 3 lNl/E N TOR ALBERT LO E/VZ %,%Z 1/2 ATTORNEVS July 7, 1959 A. LORENZ METHOD AND APPARATUS FOR CONTINUOUSLY DEGASSING MOLTEN METALS, PARTICULARLY STEEL, BY EVACUATION Filed Aug. 5, 1957 I 6 Sheets-Sheet 4 III INVENTOR ALBERT LORENZ ATM/Viki a 2,893,860 CONTINUOUSLY DEGASSING MOLTEN LY STEEL, BY EVACUATION 6 Sheets-Sheath Now INVENTO? ALBERT LORENZ ATTORNEYS July 7, 1959 LORENZ 2,893,860

METHOD AND APPARATUS FOR CUNTINUOUSLY DEGASSING MOLTEN METALS, PARTICULARLY STEEL, BY EVACUATION Filed Aug. 5, 1957 6 Sheets-Sheet 6 Fi .6 g 235 INVE/WUR ALBERT LORENZ A TTOR/VEYS United States Patent METHOD AND APPARATUS FOR CONTINUOUSLY DEGASSING MOLTEN METALS, PARTICULAR- LY STEEL, BY EVACUATION Albert Loreuz, Hanau am Main, Germany, assignor to W. C. Heraeus G.m.b.H., Hanan am Main, Germany, a corporation of Germany Application August 5, 1957, Serial No. 676,131

Claims priority, application Germany February 21, 1957 4 Claims. (Cl. 75-49) The present invention relates to a new method of expelling gases from molten metals, especially steel, by passing the same through an evacuated chamber.

The basic concept of expelling or extracting undesirable gases from metals by subjecting the molten metal to the influence of a vacuum has been known for a long time. This has been done, for example, by agitating the molten metal in the crucible under a vacuum by inductive heating means for such a length of time until it was sufficiently degassed.

Another known method consists in removing the undesired gases from the molten metal, particularly steel, before it is cast and portion-by-portion while in the casting ladle. Such degasification is carried out in an evacuated chamber and the necessary movement of the molten metal through the vacuum chamber is produced solely by gravity either by a free fall of the metal or by the rise of the barometric level of the molten metal into the evacuated chamber produced by gravity. All of these known methods have a series of disadvantages which are primarily connected with their requirement that great quantities of molten metal have to be moved back and forth. Although, these disadvantages were fully realized, they have so far been regarded as unavoidable since the difliculties of including a degasification process into the mechanical casting operation as well as the technical difliculties of degassing large quantities of steel at high temperatures did not seem to permit any other solution.

It has also been proposed prior to this invention to cast large quantities of steel in one charge into a vacuum chamber. This, however, requires extensive modifications of the technical process and special apparatus of very large dimensions, as well as very sensitive parts which are easily damaged in the rough operation of a steel foundry. Although in the production of castings of rimmed steel the advantages of a degasification of the metal by means of a vacuum have already been realized, it has so far not been possible to carry out such methods except by very expensive means and procedures.

It is the principal object of the present invention to provide a very simple and inexpensive method of degassing molten metals, and especially steel, in a vacuum without incurring any of the above-mentioned disadvantages, and in a manner so as to permit a smooth and continuous operation by means of a very simple apparatus.

It is a further object of the present invention to provide a method of continuously expelling the undesirable gases from molten metals by conveying the metal continuously into and out of an evacuated degassing chamber.

Another object of the invention is to provide a method of this type wherein a continuous circulatory flow of the molten metal from its container through an evacuated chamber above said container and back into the container may be produced by the provision of very simple means which permit the metal flowing into the evacuated chamber to be maintained therein at a level difierent from the level of the metal flowing out of the chamber.

A further object of the present invention is to provide A ice 2 a method of the mentioned type wherein the molten metal is conveyed into the evacuated degassing chamber by feeding a suitable gas or vapor into the metal.

Another object of the present invention is to provide a method of continuously degassing molten metalsby passing the molten metal into a vacuum chamber and, after the metal has been degassed therein, by returning it to the main body of metal by centrifugal force.

A further object of the present invention is to provide very simple and inexpensive apparatus for carrying out the new method and for attaining the various advantages thereof.

The degasification method according to the present invention principally consists in passing the molten metal, for example, steel, continuously from its container 'along one path into an evacuated chamber, and in then returning it to the container along another path. The apparatus for thus circulating the molten metal may be of very simple design. For producing the forces required for such circulation, the new method relies particularly upon the liquid condition and the relatively high density of the molten metal. The new method possesses all the advantages of a continuous process and although it. avoids the necessity of moving or agitating large quantities of molten metal as required in the prior noncontinuous methods, it is still capable of degassing such large quantities of metal very efliciently and within a very short time.

While a successful performance of a degasification process according to all previous methods relied entirely and at great expense upon the use of gravity, the-continuous method according to the present inventionin combination with a new apparatus for conveying or'circulating the molten metal through a vacuum chamber permits such process for the first time to be carried out practically independently of such force. gasification process according to the new method operates continuously, and the rate of flow of the molten metal through the vacuum chamber is quite fast, a very large quantity of metal may be efliciently degassed within a short time even though the quantity of molten metal actually passing at any time through the vacuum chamber might be very small. The application of a forced circulation as provided by the invention also allows considerable freedom in designing the apparatus required for; an eflicient degasification. Thus, for example, an apparatus according to the invention has been designed which may be applied successively to different parts of the-bodycf molten metal in a casting ladle or other vessel so that nearly all parts of the metal will be reached'by thev apparatus and be passed successively through the vacuum chamber and thus be degassed.

When the molten metal before being degassed flows from the ladle or other vessel along an intake conduit'upwardly into the vacuum chamber, the reduction of the density of the metal caused by the formation of gas bubbles therein will carry or drive it to a higher level than the level from which the degassed metal will flow back into the vessel along the return conduit. According to the invention, this process is started and preferably also subsequently assisted by injecting a material of considerably lower density, preferably a gas or vapor, into the molten metal while the latter flows upwardly toward the vacuum chamber. If this material consists of insoluble gases, the gas bubbles then forming within the molten metal will increase in size while rising toward and into the vacuum chamber. This material will then again easily separate from the molten metal within the vacuum chamber together with the undesired gases origie nally contained in the metal. By injecting such material, the medium density of the molten metal caused by its own gases which allows it to flow of its own accord into the vacuum chamber to be degassed therein will be still Since the de-- further reduced so that the metal will reach a still higher level in the vacuum chamber relative to the normal barometric level, that is, the level of the degassed metal. The low density material will therefore act as a carrier and convey the molten metal continuously into the vaouumchamber and produce therein the mentioned difference in levels which, inturn, results in a continuous and very eflicient degasification of the molten metal and also 'in acontinuous circulation thereof from the ladle toward and'through the vacuum chamber and back to the ladle.

If the circulating apparatus is designed so as to maintain the molten metal flowing into the vacuum chamber abaconsiderably higher level therein than'the metal flowing out of the-chamber, the entire contents of the container or ladle holding the main mass of molten metal will'be-gradually and continuously passed through the vacuum chamber and thus be thoroughly degassed thereineither in the form of a thin layeror stream or in the form ofsmall droplets.

the molten metal itself has a high gas content, the gas "bubbles forming in the metal of their own accord may 'beutilized for-continuously conveying the metal into the-'vacuumchamber. In such a case, 'itwill only be 'necessaryto start the proper flow by an initial insertion of'supplementary gas or,"'after-such start, merely to assistthecontinued flow by feeding a small stream of such gasinto'the'rising metal. Also, if the degassing operation has been interrupted or the automatic formation of bubbles of'the gases inherent in the rising metal diminishes, it may again become necessary to feed the extra gas either temporarily or continuously into the fiiolten metal. 1

The present invention may also be modified by applyiog' 'a circulating apparatus which assists in the discharge of 'thedegassed metal from the vacuum chamber. In such'event, the relatively high density of the molten'metal itself may be utilized to considerable advantage for producing a" centrifugal force for conveying the metal. Such centrifugal force may easily be made of sufficient size even" t hough the necessary rotating parts of the apparatus are of small diameters and are driven at low speeds a the means for conveying the molten metal are furthermone applied to that part of the circuit where the degassed metal is returned to its container and not to that part where the metal before being degassed is conducted into the vacuum chamber, the amount of metal conveyed and'the resistance to the flow thereof within such circuit'may' be controlled so that the level of the returning molten metal in the vacuum chamber will be lower than the level which would correspond to the difierencein pressure between the outer atmosphere and that within the vacuum chamber. i

The degasification apparatus according to the invention therefore' essentially consists of a vacuum chamber which 'is disposed above the container holding "the molten metal and is connected thereto by two separateeonduits; and a mechanism for conveying the metal continuously from the vacuum chamber back into the container.'-'Due to such forced circulation, the apparatus itself-may be made of a relatively'small size. This, in turn, renders the generation of the centrifugal forces utilizedfo'r effecting the circulation avery' simple matter. These forces may, for example, be generated bysecuring the"'r'eturn"conduit of the molten metalto' the bottom of the vacuum chamber and coaxially -thereto,by"prjo viding' the lower end of this conduit with a disklike member'of al'arg'er diameter,--by immersing" this lower end of the return conduit, as well 'as the intake conduit, which ertj'ends within the return conduit andcoairi'ally thereto into"'=the"rnolten metal within thekontainers, and by rotating "the vacuum chamber togethefwifih "the return conduit withinthemolten metal. The de assed metal returflingflf'rom the vacuum chamber and arriving at the disklike member at the lower end of the return conduit will then be expelled therefrom into the surrounding metal in the container by the centrifugal force produced by the rotation.

The circulating mechanism therefore consists of two parts, a mechanical part and a functional part, the mechanical part consisting of the disklilte end of the return conduit within" the container holding the body of molten'metal; andthe functional part consisting'of the rotation of the vacuum chamber together with the return conduit. The interaction of these two parts results in a highly effective and simple circulating mechanism.

Further objects, features, and advantages of thepresent invention will be apparent from the following detailed description thereof, particularly when read with reference to the accompanying drawin'gs, in'which-- Fig. 1 shows, largely in cross section, an apparatus according to the invention in which'the molten metal is conveyed into the vacuum chamber by means of a supplementary gas fed into the metal;

Fig. 2 shows a similar view of a modification of the apparatus illustrated in Fig."l;

Fig. 3 shows a similar view of another apparatus according to the' invention in which the molten metal is returned from the vacuum chamber into the container by means of centrifugal force;

Fig.4 shows partly in cross section a detail view of a modified portion of the apparatus according to Fig. 3;

'Fig. 5 shows, partlydiagrammatically, a-g'eneral view of an entire degasification-plant according to the invention during its operatiomwhile 1 "Fig; 6'shows a view similar to Fig. 5 but with the degasification apparatus intheinoperative position.

"Referringto'the drawings, and first particularly to Fig. l, a vacuum pump 1 isconnected to a vacuum chamber 2 by a pump line 3. 'Vacuum chamber 2. 'is formed by a tank 4 having a bottom 5 to which short pipes 6 and 7 are connected which are adapted to be partly immersed into themolten metal 8 within a container or casting ladle 9. This-ladle 9'has a lining'lll and a taphole 1 1' which is adapted to beclosed from above by means of a plug 12.

After the apparatus is lowered into ladle 9 so that the lower'ends of pipes 6 and'7 are immersed into the molten metal8 to a point below the surface 13 thereof, chamber 2 is evacuated whereby the molten metal rises Within'pipes 6 and 7 'to the barometric level h A'pipelin'e 14 is adapted to" be inserted into the molten metal 8 in ladle 9 so that its end 15 is disposed at a point'closely underneath or within the lower end of pipe 6. Pipe line 14 is connectedto'a source 'of supply of a suitable gas, not shownja'nd adapted'to conduct such gas into the molten metal 'in'pipe 6. The gas bubbles will then rise in pipe 6 and, in the course oftheir ascent, they will increase "in size. They have the tendency to take along the molten metal in "pipe 6 into'vacu'um chamber 2 in the direction as shown by the 'arrow 17. These gas bubbles reduce thejdensity'of'the molten metal in pipe 6, thereby causing the metal to rise to a higher level than the barometric level h of the solid metal column in pipe 7. The metal thus enters from pipe 6 into vacuum chamber 2 in which the added gas is separated from the meta], 'whilethe undesired gases contained therein 'are likewise expelled. The molten metal then'fiows in thedirectionsh'ow'n byarrow 18 toward and into the return pi pefi andithe n back tothe main body of metal 18in ladle 9. In order to prevent the molten metal fromsplashing too upwardly nits chamber 2, a stationary=deflectirigplate -20 may lie-provided within chamber 2" atfa "certain height above the mouth of pe 6. .1-

In the embodiment. of the invention. as shown in Fig. 1, pipeline 13,15 through which the conveying gas is supplied into the moltemmetal in the intale pipe 6, forms a rspace arm: se a at w h. a s 4 and pipes 6 and 7. This pipe line is adapted to be removed from ladle 9 after the flow of molten metal in the direction of arrows 16, 17, 18, and 19 has been started by the added gas, provided the molten metal itself contains sufiicient gas or still contains the same to maintain the flow after such start or after the degasification has been carried out for a certain length of time. When the gas content of the molten metal in ladle 9' has been diminished to such an extent that the continued automatic circulation without the addition of supplementary gas will be interrupted or is soon liable to cease, pipe line 14, is reinserted into pipe 6 to start the flow or to assist it by a further supply of conveying gas.

Fig. 2 illustrates a modification of the apparatus shown in Fig. 1. In this'case, the gas line 21, 22 is secured by a vacuum-tight connection to vacuum tank 4 and extends centrally from above through the intake pipe 6, terminating at or near the lower end thereof. 1

vThe added conveying gases may consist of any suitable inert gases, for example, argon, which are not solubl'e or only slightly soluble in the molten metal. However, other gases such as those contained to some extent in the molten metal itself, for example, nitrogen and carbon monoxide, may also be used with equal results since they are separated in any event from the molten metal within the vacuum chamber.

In certain cases it is also possible to combine the introduction of gas for conveying the molten metal into the'vacuum chamber with additional purposes. Thus, for example, if iron or steel are to be degassed, the introduction of oxygen into the molten metal will assist in carrying out the necessary refining process thereof.

The vacuum chamber may also be provided with additional means for efiecting or facilitating the separation of the gases from the metal which usually splashes around in the chamber in the form of large drops or jets. A simple form of such means may consist of the deflecting plate as shown in Figs. 1 and 2. However, these separating means within the vacuum chamber may also consist of moving elements, for example, a revolving plate or the like.

However, the important feature of the method as above described is that it does not require any movable parts, and particularly'no rotary movement of the apparatus, but that it only relies upon the buoyancy of a mixture of gasand molten metal for conveying the metal into and through the vacuum chamber. This method is thereforeof greatest simplicity and may be carried out by means of a very simple and inexpensive apparatus. Fig. 3 illustrates a modification of the invention which relies upon the same basic principle as the embodiments shown in Figs. 1 and 2, namely, of effecting a constant circulation of the molten metal through the vacuum chamberand of thus attaining a continuous gasification of the metal by producing a difference in density of the molten metal within the intake and return pipes of the vacuum chamber. However, instead of reducing the density of the metal within the intake pipe so as to raisetheintake level of the metal relative to the normal barometric level h that is, the-level within the return pipe, by injecting an extra gas into the metal within the intake pipe, the modification according to Fig. 3 relies upon the principle of lowering the level of the surface of the degassed metal within the vacuum chamber relative to the normal barometric level h. by means of centrifugal force.

-- The apparatus for carrying out this method, as illustrated in Fig. 3, consists of a vacuum pump 101 which 105 carries suitable bearing means 107 for rotatably supporting a container 108 which forms the main vacuum chamber. leakage of outside airin to containers 105 and 108 is prevented by providing sealing rings 109 and 110, as well as an annular chamber 111' between the outer wall surface of the reduced neck portion 112 of container 108 and the inner surface of container 105, and by connecting such chamber 111 to vacuum pump 101 by means of a pipe 113 so that vacuum chamber 108 will be continuously evacuated.

, Vacuum chamber 108 and its upper tubular end 112 may be rotated by a motor 114 through reduction gears 115, for example, in the direction asshown by arrow 116.

The walls of vacuum chamber 108 may also have a lining (not shown). The substantially parabolical bottom portion 117 of container 108 has a tubular 118 portion secured thereto which may either be a solid pipe or be likewise lined. This tubular portion 118 carries coaxially thereto an inner pipe 119 by means of spacing members 120. The upper end of pipe 119 extends for a cerdistance into container 108.

The lower ends of the coaxial pipes 118 and 119 extend into a container or casting ladle 121 and are immersed into the molten metal 122 for a certain distance below the surface 123 thereof. Laddle 121 is provided with a lining 124 and a taphole 125 which may be closed from above by a plug 126. Below the surface 123 of the molten metal in ladle 121, the outer or return pipe 118 terminates in an annular disklike member 127, thus forming an annular passage between disks 127 and 128 which communicates with the return passage in pipe 118. The two disks 127 and 128 may be further secured to each other in the proper spaced relation by spacing members 129 which divide the annular passage into a plurality of separate channels which improve the return flow of molten metal into the main body of metal 122 in ladle 121 as subsequently described.

The lower end of the apparatus consisting according to Fig. 3 of the coaxial pipes 118 and, 119, disks 127 and 128, and the spacing and supporting members 120 and 129 may also be made of highly refractory ceramic material, as illustrated in Fig. 4. The reduced lower end 130 of vacuum tank 108 which may have a lining 131 merges intothe ceramic part132, and these two parts are preferably disconnectable from each other in a suitable manner, not shown. The ceramic part 132 consists of the central intake channel 133 and a plurality of vertical return channels 134 surrounding the intake'channel 133 and terminating at the-lower ends in radially extending outlet channels 135 having outlet openings 136. When the vacuum tankp108 is rotated, the molten metal contained in the radial channels 135 produces the centrifugal force which effects the continuous movement of the'metal from vacuum chamber .108 into the main body of metal 122 in ladle 121. i

For carrying out the method according to the invention, the degasification apparatus is lowered into the molten metal 122 in ladle 121 substantially to the position as shown in Fig. 3 and is then evacuated by pump 101. The metal will then rise into vacuum chamber 108 until it reaches a level of a height h which corresponds to the barometric pressure attained at the respective degree of exacuation which for steel amounts to a maximum of approximately cm. Motor 114 is then switched-on so as to rotate vacuum tank 108 and the coaxial pipes 118 and 119 with disks 127 and 128 thereon.

The revolving disks 127 and 128 with the spacing members 129 transmit their movement to the intermediate amount of molten metal which is then thrown outwardly in the direction shown by arrows 137. The velocity of the throw depends upon the speed of revolution and the diameter of disks 127 and 128 since these two values aside from the density of the molten metal determine the power of the centrifugal force. For practical purposes, the disks are preferably made of a diameter of approximately 50 cm. and the speed is made 1 to 3 revolutions per second. 7,

The amount of molt n metalv thrown out between'disks 127 and 128 or outlet openings 136, as shown in Fig. 4, respectively, is continuously replenished by the flow of metal from vacuum chamber 108 through pipes 118 and 119 in the direction shown by arrows 138 and 139. Since the barometric pressure allows the molten metal to penetrate into chamber 108 up to the level h the metal will continue to flow into and through intake pipe 119 in the direction of arrows 138 since within this central pipe it will be only very slightly affected by the centrifugal force produced by the rotation and acting in direction 137 vertically to the direction of new 138-139.

If the speed of rotation, the diameter of disks 127 and 128, and the resistance to the flow within intake pipe 119 are all made of the proper size, the level of the molten metal within vacuum chamber 108 will be lowered a substantial extent below the normal barometric level h forexample, to the level h Thus, there will no longer be a uniform surface which connects the inner intake flow with the outer return flow of the metal. This has the great advantage that the metal will how very quickly through chamber 108 and result in a free flow therein which insures a very efiicient degasification of the metal.

Since the molten steel rising through the inner pipe 119 contains considerable quantities of gases which even under standard conditions may amount to a multiple of the volume in metal, the enclosedgases will normally urge toward the surface within the vacuum chamber, thereby taking along themetal. Since the pressure upon the metal progressively decreases as the metal rises to a higher level within the intake pipe 119, the enclosed g'a'ses will separate with increasing intensity. This results in the formation of gas bubbles which more and more increase in volume as they are reaching a progressively higher level, thus pushing the metal above them into the vacuum chamber. These gas bubbles when finally bursting within the vacuum chamber also finely distribute and scatter the metal into small particles. The molten metal will thus attain a very large'surfaee area within the vacuum chamber, be more extensively subjected to the action of the vacuum, and be thoroughly degassed. Since, on the other hand, the metal in return pipe 108 is fully degassed and, except for its return flow, perfectly quiet, the difierence between the height ofthe intake and return levels will be very considerable.

The mentioned fine and thorough distribution of the molten metal within vacuum chamber 108 may be further increased by making the intake pipe 119 of a height so as to extend above the level h but not to reach the barometric level h The metal will thus be freely ejected at a high velocity from the mouth of pipe 119 in the upward direction and be more thoroughly exposed to the vacuum by its fountainlike flow within chamber 108. In order to prevent the molten metal from being shot upwardly into the upper'sta'tionary tank 105 and from entering into the pump line 104, a deflecting plate 140 which is capable of resisting the high temperatures of the molten metal is mounted within chamber 108. The upper end of intake pipe 119 may also have an annular projecting flange 141 or be provided with slots or other suitable means in order to increase its distributing action upon the molten metal.

Fig. diagrammatically illustrates the entire degasifi cation plant according to the invention with all of its essential parts. The pump unit 201 is connected by a movable vacuum pipe 202 with articulated joints 203 to the dust separator 204 which, in turn, is connected by'means of a suction pipe 205, which also serves as a supporting beam, to a head 206 similar to member 100 in Fig. 3 whichsupports the rotary vacuum tank 207 and is connected thereto by rotary bearing and sealing "means 208. A motor 209 is connected by reduction gears or a chain drive 210 to vacuum chamber 207 to rotate the same. Chamber 207 carries at its lower part the two coaxial pipes 211 and 212 which terminate in a disklike member 213 with openings 214 which communicate with the space intermediate pipes 211 and 212 8 and thus with the inside of chamber 207. The lower end of this apparatus with the disklike member 213 thereon is immersed from above into the molten metal 215 within a'ca'sting ladle 216.

Suction pipe 205 which also serves as a supporting beam for carrying vacuum chamber 207 and all the parts connected thereto is pivotally mounted on an upright 217 by means of a pair of bearing brackets 218 and a pivot shaft 219. Upright 217 is vertically slidable within a cylinder 220' and adapted to be raised and lowered by hydraulic means within cylinder 220. A guard plate or partition 221 mounted on the upper end of upright 217 protects the various elements at the right of ladle 216 and vacuum tank 207 as Well as the operator from the heat radiated from the ladle and tank and any possible molten metal particles spattering out of ladle 216.

Cylinder 220 is mounted on a platform 222 which also supports a pair of beams 223 at the right side of upright 219 which are connected at the upper end and above suction pipe 205 by' a crossbar 224. Platform 222 further supports a hydraulic pump unit 225 for raising and lowering upright 217' with suction pipe 205 and all of the elements connected thereto and for there by also pivoting suction pipe 205 and all of these elements about the pivot 209. A control panel 226 with an operators stand is also mounted on platform 222 which is provided with wheels 227 which may be driven by a motor 228 to move the entire apparatus on rails 229 relative to ladle 216.

Fig. 6 finally illustrates a degasification plant with a vacuum tank similar to that shown in Fig. 2 and an operating mechanism similar to that shown in Fig. 5 but in a position prior to thedegassing operation. The upright 217 is then hydraulically elevated, whereby the suction pipe 205 bears against crossbar 224 and is pivoted about shaft 219. Vacuum tank 230 is thus likewise raised and pivoted. After platform 222 is moved to the proper position relative to the casting ladle 216, upright 21'! is lowered, whereby vacuum tank 230 is pivoted to its vertical position and its lower end immersed into the molten metal in ladle 216. Vacuum tank 230 is mounted on suction pipe 205 and consists of the main chamber 231 with an intake pipe 232 and a return pipe 233 at the lower end of chamber 231 and a bottom 234 of chamber 231 which inclines downwardly from pipe 232 toward pipe 233 to facilitate the return flow. A feed pipe 235 which is connected to a supply of a suitable gas (not shown) extends through chamber 231 and centrally through intake pipe 232 to a point near the lower end thereof.

A detailed description of the operation of vacuum chambers 207 and 231 as shown in Figs. 5 and 6, respectively, has already been given above and therefore needs not be repeated.

Although my invention has been illustrated and described with reference to the preferred embodiments thereof, I wish to have it understood that it is in no way limited to such particular embodiments or to the details thereof, but is capable of numerous modifications within the scope of the appended claims. The important concept of the present invention as defined by these claims is to provide a method and a suitable apparatus for continuously conveying the molten metal into a vacuum chamber to be degassed therein and then to return it to its container by producing a noticeable difference in the level of the molten metal fed into the vacuum chamber and the level of the molten metal within the chamber which is ready to be removed therefrom. The two different methods as described above may also be combined with each other in that a supplementary conveying gas may be fed into the intake pipe 118, 133, or 212, as shown in Figs. 3, 4, or 5, respectively. The particular means for carryingout the conveying movement of the moltenmctal into and fromthe vacuum chamber may also be of a different type and design than shown in the drawings and above described. Thus, for example, it is possible to use an electro-magnetic pump which moves the molten metal by means of an electric current within a magnetic field. The apparatus according to the invention also have the great advantage that they may be made of a mobile construction and be easily moved from one casting ladle to another, and that they are movable and pivotable and thus capable of reaching almost any part of the body of molten metal Within a casting ladle.

Having thus fully disclosed my invention, what I claim as new is:

1. An apparatus for continuously degassing molten metals comprising a container adapted to hold a body of molten metal, a chamber disposed above said container and having an intake conduit and a return conduit at the lower end thereof adapted to be partly immersed into said body, a substantially circular outlet member on the lower end of said return conduit and coaxial thereto, said outlet member having a diameter larger than the diameter of said return conduit and having a plurality of substantially radially extending outlet channels therein, means for continuously evacuating said chamber when said conduits are immersed in said body, and means for rotating at least said outlet member, whereby when said outlet member is rotated within said body of metal, the molten metal contained within said channels will be subjected to a centrifugal force and be ejected from said channels into said metal body, thereby producing a circulation of said molten metal from said body through said intake conduit into said chamber to be degassed therein and back through said return conduit and said outlet member into said metal body.

2. An apparatus as defined in claim 1, further comprising means for injecting a gaseous material into said intake conduit near the lower end thereof.

3. An apparatus for continuously degassing molten metals comprising a container adapted to hold a body of molten metal, a chamber disposed above said container and having an inner intake conduit and an outer return conduit coaxially with said chamber within each other and secured to the bottom of said chamber, a pair of annular disklike members of a larger diameter than said outlet conduit and coaxial with said conduits, one of said members being secured to said intake conduit near the lower end thereof and the other member being secured to the lower end of said outlet conduit, means for continuously evacuating said chamber when said disklike members on said conduits are immersed in said body, and means for rotating said chamber with said conduits and members whereby when said disklike members are immersed in said body and when said chamber with said conduits and members are rotated, the rotation of the molten metal between said members produces a centrifugal force for ejecting the molten metal from said return conduit into said metal body and thereby produces a circulation of said metal from said body through said intake conduit into said chamber to be degassed therein and back through said return conduit into said metal body.

4. A method of continuously degassing molten metals comprising the steps of continuously evacuating a chamber disposed above a container and directly communicating with a body of molten metal in said container by a pair of conduits disposed coaxially around each other, connected to the bottom of said chamber and partly immersed into said body of metal, conducting the metal through the inner conduit into said chamber to be degassed therein, and rotating at least the outer conduit about its axis so that the degassed metal within said outer conduit will be subjected to a centrifugal force and by the action of said force be continuously withdrawn from said chamber and ejected into said body of metal, wherein said centrifugal force is produced by the lower end portion of the rotating outer conduit which is submerged in said body of molten metal and separates the metal within said end portion into a plurality of substantially radially extending bodies and then passes the metal to a plurality of streams into said main body of molten metal.

References Cited in the file of this patent UNITED STATES PATENTS 291,223 Pielsticker et a1. Ian. 1, 1884 1,921,060 Williams Aug. 8, 1933 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,893,860 July '7, 1959 Albert Lorenz It is herebfi certified that error appears in the-printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 6, line 17, for "cer-" read certain line 22, for "Laddle" read Ladle line 60, "exacuation" read evacuation Signed and sealed this 29th day of December 1959.a

SEAL) ttest:

KARL AXLINE ROBERT c. WATSON Attesting Oificer Commissioner of Patents 

4. A METHOD OF CONTINUOUSLY DEGASSING MOLTEN METALS COMPRISING THE STEPS OF CONTINUOUSLY EVACUATING A CHAMBER DISPOSED ABOVE A CONTAINER AND DIRECTLY COMMUNICATING WITH A BODY OF MOLTEN METAL IN SAID CONTAINER BY A PAIR OF CONDUITS DISPOSED COAXIALLY AROUND EACH OTHER, CONNECTED TO THE BOTTOM OF SAID CHAMBER AND PARTLY IMMERSED INTO SAID BODY OF METAL, CONDUCTING THE METAL THROUGH THE INNER CONDUIT INTO SAID CHAMBER TO BE DEGASSED THEREIN, AND ROTATING AT LEAST THE OUTER CONDUIT ABOUT ITS AXIS SO THAT THE DEGASSED METAL WITHIN SAID OUTER CONDUIT WILL BE SUBJECTED TO A CENTRIFUGAL FORCE AND BY THE ACTION OF SAID FORCE BE CONTINUOUSLY WITHDRAWN FROM SAID CHAMBER AND EJECTED INTO SAID BODY OF METAL, WHEREIN SAID CENTRIFUGAL FORCE IS PRODUCED BY THE LOWER END PORTION OF THE ROTATING OUTER CONDUIT WHICH 